The Burning Edge points out that you can now search in textboxes and textareas in a webpage when you do a "Find in this page" search. The corresponding bug is bug 58305 and this enhancement appears in builds on and since 2004-04-16. I sorely missed this, especially so because IE does have this feature - some sites use textareas to display code.

Screenshot of Find in this page in textarea

As pointed out in this comment, this works for both the "Find in this page" function (accessible via Ctrl-F or Edit -> Find in this page...) and the "Find as you type feature". But with "Find as you type", the text found is not highlighted due to bug 134586 - selection in text field is invisible when it doesn't have focus. This will probably be fixed by the time Firefox 1.0 is released.